Summary The Cessna T207A (registration C-GGQR, serial number 20700499) departed from Pemberton Airport, British Columbia, at about 1500Pacific daylight time on a visual flight rules flight to Edmonton, Alberta. The aircraft initially climbed out to the east and subsequently turned northeast to follow a mountain pass route. The pilot was alone on this aircraft repositioning flight. The pilot had been conducting air quality surveys for Environment Canada's Air Quality Research Section in the Pemberton area. The aircraft was operating on a flight permit and was highly modified to accept various types of probes in equipment pods suspended under the wings, a camera hatch type provision in the centre belly area, and carried internal electronic equipment. About 30 minutes after the aircraft took off, the Coastal Fire Service responded to a spot fire and discovered the aircraft wreckage in the fire zone. A post-crash fire consumed most of the airframe, and the pilot was fatally injured. The accident occurred at about 1506Pacific daylight time. Ce rapport est galement disponible en franais. Other Factual Information Wreckage and Site The aircraft struck the trees in a left descending turn with an excess of 30degrees of bank. The wreckage trail was oriented on a heading 180degrees from the original flight path. Following impact with the ground, the aircraft slipped down the steep mountain slope, was turned around to face the direction of entry into the trees, and came to rest on its right-hand side. During the initial impact with the trees, an outboard section of the right horizontal stabilizer sheared from the empennage. Equipment pods containing lasers separated from the wings and were found about 50feet back from where the wreckage came to rest. Decals affixed to the exterior of the laser probe pods were marked "DANGER" and warned of laser radiation when opened. The laser devices were electrically disconnected for this particular flight. The engine remained precariously attached to the firewall. Most of the aircraft structure was consumed by a post-crash fire. This destruction limited the analysis of flight controls and instrumentation. Two of the three propeller blades were fractured in overload about four inches from the tips. The three propeller blades exhibited leading edge damage, chordwise scoring, and torsion damage, all indications of applied power. The emergency locator transmitter (ELT) was destroyed by the impact and fire, and no signal was received. Present standards do not require that ELTs resist crash damage. Weather The weather at Pemberton on the day and time of the occurrence, recorded by an automatic weather reporting station, was as follows: clear skies; wind 110true(T) at 4knots; temperature 28.6C; dew point 5.3C; remarks: sea-level pressure 910hectopascals. The barometric pressure by which the pilot would set the altimeter was 29.80inches of mercury. The airport elevation is at 670feet above sea level (asl). The density altitude at this location was equivalent to 2682feet. Official sunset was at 2136 Pacific daylight time.1 Mountain weather is subject to its own systems and particularities. Strong rising air currents form when the hillside slopes are heated up by the sun, and descending currents form when the slopes are subjected to shadows and cooling air. This cooling of air in shadowed areas and the cooling of air above snow-covered surfaces causes downdraughts, also known as katabatic wind in mountainous areas. These phenomena can create heavy turbulence in narrow mountain passes. A rotor is a large closed eddy that forms in the lee of a mountain range, or any obstacle in the airflow, and is an area of severe turbulence. Rotors are usually found under the crests of mountain waves, often within 3000feet vertically of the generating ridge. The wind below the rotor will be in the reverse direction to the general flow. Updraughts and downdraughts in a rotor have been measured at over 5000feet per minute (fpm). The presence of rotors in this occurrence could not be confirmed. Flight Planning The flight was conducted under visual flight rules (VFR). There is no requirement to file a flight plan, and it is unclear if the pilot had formally assigned a person responsible for flight following. Consequently, full details of the flight could not be ascertained. The pilot elected to follow the Duffy Lake road mountain pass route, along Joffre Creek, at the north end of Lillooet Lake. This mountain pass route has a steep, climb section over the first four nautical miles (nm), rising to 4200feet at ground level in the valley. The altitude or alignment of the aircraft during the climb could not be determined because there was no radar coverage. There were no data available from any navigational aids. There is a VFR route along the Anderson Lake Valley that provides a much less steep and more graduated climb with a floor elevation limited to about 1400feet, just north of the airport (see AppendixA). The TSB Engineering Laboratory performed a terrain shadow analysis (TSB Engineering Laboratory report LP065/2006). The accident site location corresponds to a narrowing point at the initial climb section, with the valley about one mile wide at this elevation. This site, on the left side of the valley (southeast-facing slope), was in a large shadow region and had been for a couple of hours before the accident. The mountain peaks in the vicinity of the accident site vary in height between 9150feet and 8550feetasl, and there was some snow at higher elevations. The wreckage site coordinates, latitude 5020'N and longitude 12234'W, correspond to an elevation of approximately 3280feetasl. Using the standard lapse rate of 2C per 1000feet of elevation, the outside air temperature at the accident site at about 3500feetasl would have been 23.1C. By extrapolation, the density altitude 1000feet above terrain elevation, assuming a minimum safe altitude above ground elevation and 21.1C, would be equivalent to about 6319feetasl. The Civil Aviation Authority (CAA) of New Zealand published a Mountain Flying booklet about good aviation practices. Flight training schools also offer guidelines for mountain flying. These guidelines suggest procedures to follow when entering a valley. The guidelines are not quoted verbatim. The pilot should check with the compass and map to ensure the correct valley is being entered, and know whether the valley climbs and what altitude will be required to clear the pass or ridge at the end. It is recommended to fly in smoother, updraughting air. If a 180-degree turn becomes necessary, it is made into the wind, requiring less distance over the ground. However, downdraughts may be encountered on the lee side of mountain terrain. Always position yourself in a valley so that you will have enough room to turn around if needed. You need 5to 7.5seconds to see, evaluate, decide, and execute. If you are sinking and at low level, this time plus any time taken to move over in the valley will be longer than you have. Leaving maximum room to turn also means less bank angle is needed, therefore less wing loading and lower stall speeds. When executing the turn, control the speed; too much power translates into too much speed, which results in a greater radius. A commonly accepted minimum safe altitude in mountainous regions is at least 1000feet above the valley floor. Furthermore, minimum safe altitude on low-level flights in canyons is at least 2000feet when downdraughts are expected. Wind strength and direction can vary markedly with height. At low level, the wind may be down a valley, while nearer the tops of the ridges, it may be across the valley. Pilots are advised to fly on the sunlit side of the valleys to benefit from rising air currents. Pilot The pilot held a valid Canadian commercial pilot licence issued by Transport Canada (TC). The licence was endorsed for all non-high-performance, single- and multi-engine land and sea aeroplanes and for an instrument rating. The pilot had accumulated approximately 1500flying hours on light, single-engine aircraft, including the CessnaT207A, and had flown this particular aircraft at high weights for approximately 75hours during the five weeks preceding the accident. The occurrence pilot had been provided with a six-page Pilot's Notes document describing all of the changes to the aircraft and appropriate operating techniques. The pilot had also received training on the modified aircraft in its least favourable configuration. A description of the pilot's recent work schedule indicated that his schedule was within TC work and rest limits. Company records indicate that he had recently completed a mountain flying course. In-class topics of study included the following: mountain winds and weather, aircraft performance and manoeuvres, airmanship and pilot decision making, and mountain navigation and flight planning. There was a practical mountain flying component to this training performed in a Cessna172, but it was very limited in scope because of the risks involved. A similar occurrence (TSB report A03P0199) highlighted some of the risks involved in mountain flying training with aircraft in real conditions. TC does not issue a rating/endorsement for mountain flying training. There are no standards established to ascertain the proficiency of a pilot in this environment. Pilots who complete a mountain flying course may not acquire the required skill sets. The pilot showed an interest in photography. He had recently acquired a film camera, which he had used in flight on at least one previous occasion. The camera was found near the pilot's body at the accident site. An autopsy of the pilot, including a full toxicology examination, did not reveal any condition that could have led or contributed to the accident and revealed that the pilot suffered post-crash-related fatal injuries. The extent of destruction caused by the impact with the ground and the subsequent fire precluded any valuable analysis in the severity of the pilot's injuries. Human Factors - Illusions The most accurate sensory information available to a pilot about aircraft attitude and motion are the visual cues provided by the earth's horizon, the aircraft's flight instruments, or both. The CAA of New Zealand Mountain Flying booklet describes common illusions a pilot may experience. The illusion of Relative Scale explains that, when you are amongst large mountains, it is very difficult to accurately judge scale and distance. Mountains seem a lot closer than they actually are, simply because they are so much larger than you are. The only way to confirm your distance from the terrain is by picking out features on the surface, such as tussocks, trees, or bush that your mind can accurately judge the size of. This will help you work out how far away you are and give you an indication of your size relative to the mountain. It is important to be able to judge your distance from the terrain and it is a required skill to determine if you have allowed enough room for a reversal turn. The booklet describes the False Horizons illusion that occurs because of the frequent lack of a defined external horizon, which can create aircraft attitude and airspeed problems. When flying amongst the mountains or anywhere the horizon is not visible, the pilot must imagine that horizon. Relying on the aircraft instruments alone will not work. In a confined space with reduced visibility, the eyes must be outside and performance must be interpreted by aircraft nose attitude and then confirmed by instruments (instrument discipline). Inexperienced pilots often fall into the common trap of using a ridgeline as the horizon and unintentionally altering the aircraft attitude, climbing the aircraft with a corresponding decrease in airspeed, and not making a timely decision to reverse course. The horizon goes through the base of the mountains, not the ridges. The Contrast illusion may also exacerbate this situation by creating a blending of ridgelines in the distance. Aircraft The Cessna T207A, a "normal category airplane,"2 is certificated under Federal Aviation Administration (FAA) Type Certificate Data Sheet A16CE. Airworthiness standards for the issue of type certificates, and changes to those type certificates, for aircraft in the normal, utility, aerobatic, and commuter categories must be met. An operator may apply and TC may issue a limited supplemental type certificate (LSTC) for a specific serial numbered aircraft, provided that compliance is demonstrated with the applicable airworthiness standards. Subsections511.13(1) and 513.07(1) of the Canadian Aviation Regulations (CARs) require that the applicant for a change to a type design meet the latest standards. A TC-delegated design approval representative (DAR) modified this aircraft and reported that the aircraft met the rate-of-climb requirements. Climb gradient calculations and/or testing were not completed for the modified aircraft, and for this reason, the aircraft could not be approved for an LSTC. The DAR elected to submit an application to TC for the issue of a "flight permit- specific purpose." A "flight permit- specific purpose" may be issued for an aircraft that does not comply with applicable airworthiness standards, that is, Paragraph523.65(a),3 but is deemed capable of safe flight. TCissued a "flight permit- specific purpose" for the occurrence aircraft. This authority was subject to conditions/limitations, and was granted for temporary purposes.4 It is intended to permit flight testing in order to show compliance with the latest airworthiness standards in the case of a modification to a type design. It was originally issued on 14July2005 for the purposes of evaluating the environmental equipment installed and was valid for a period of 60days from this date. A similar flight authority was reissued on 18July2005 and was valid until 18ugust2005. Meanwhile, a concurrent flight authority, a "flight permit- ferry flight" for the purpose of conducting atmospheric research following modification of the T207A, was issued on 10August2005 and was valid until 31October2005. On 15November2005, a "flight permit- ferry flight" granting the flight authority for the purpose of conducting atmospheric research was renewed; it was renewed again on 08 March 2006 and was valid until 31July2006. The aircraft was highly modified to accept four wing-pylon-mounted canisters/laser pods, a roof sample collection probe, and a camera hatch type provision in the centre belly area. It had a Horton STOL-Craft Inc. short take-off and landing (STOL)5 modification kit installed (supplemental type certificate [STC] SA1328CE), a Hartzell propeller Model PHC-C3YF-1RF installed as per STCA696AL, and it carried electronic computer equipment and apparatus mounted in metal frames, secured as cargo to the aircraft floor. It had been operated at a maximum allowable take-off weight increased to 3955pounds in accordance with a document proposed by the DAR. To power all this equipment, a 28-volt, 200-amp alternator was adapted to the engine. An Environment Canada observer would operate this equipment to conduct atmospheric research in flight. The equipment was not operated during this repositioning flight; therefore, there would not have been an additional power requirement from the engine. A flight test was performed by the DAR to verify that the aircraft could be flown safely in this configuration, and to assure that the engine cooling was adequate while in the climb and producing the required project electrical power (see flight test data at appendices B and C). The occurrence pilot had been instructed to not climb the aircraft too hard. The test flights for certification were to be done at a later date when applying for the LSTC. There is no requirement to placard such an aircraft as is the case for restricted category or experimental aircraft. Engine and Fuel System Examination During examination of the engine (Teledyne Continental TSIO-520-M, serial number291708R) following the occurrence, a deposit plugging various parts of the fuel system was observed. It was noted that the substance was constricting the flexible fuel supply line and obstructed the inlet fitting to the distributor. Scanning electron microscope (SEM) comparison analysis found no match to the parent material of the flexible fuel hose and fire shield cover. Climb performance would have been degraded further by a fuel system constriction and reduction of power available; therefore, further analysis was commissioned to identify the substance and determine whether the obstruction was a result of the post-crash fire. The deposit was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) [Powertech file 06025.GRA, Project 12272-43-06]. The infrared spectrum of the deposit resembled that of polyethylene terephthalate (PET), a thermoplastic material that originates from the reinforcing fibres in the fuel line. The material was deposited as a result of the post-crash fire. There was sufficient fuel on board for the flight. A fuel sample retrieved from the primary refuelling source for this aircraft during the course of the missions was retrieved and analyzed. The sample corresponds to aviation fuel 100LL and was clear of contamination. Performance Weight and balance calculations performed during the investigation indicated that, at take-off, the aircraft weighed approximately 3618pounds. This was 182pounds below the aircraft's original maximum gross weight of 3800pounds, and 337pounds below the new maximum allowable take-off weight of 3955pounds. This weight increase was allowed by the DAR as stated in a document referred to as the Pilot's Notes, document CN-MSC-011, also referred to as a flight supplement that was to be incorporated to a flight permit authority. A review of TC documentation provided did not reveal the incorporation of this document to any of the flight authorities issued. The centre of gravity (CG) at take-off was calculated to be 42.88inches aft of the datum. The aircraft had been fuelled to full tanks. Information provided by the manufacturer indicates that this would constitute 36.5US gallons in each tank. The occurrence flight duration was about six minutes and the fuel burn was five gallons, which included start, taxi, take-off, and climb. The aircraft weight at the time of the accident was calculated to be 3588pounds and the CG at 42.84inches aft of the datum, within the allowable range. Records show that the aircraft was serviced and maintained in accordance with existing directives. The aircraft was manufactured in 1979and had flown a total of 13900hours before the accident flight. A review of the journey, airframe, engine, and propeller logbooks showed nothing remarkable. The engine was operated "on condition," and had accumulated about 2450hours since overhaul. The maintenance logbooks contained no uncorrected deficiencies. The Cessna T207A is a fuel-injected turbocharged engine capable of maintaining maximum engine climb power up to 17000feet. The pilot operating handbook (POH) indicates that the normal climb- 95KIAS, flaps up, 2500rpm, 30-inch of manifold pressure (MP), cowl flaps open, and standard temperature- gives 500fpm at about 6319feet density altitude. The best or maximum rate of climb for this aircraft is achieved with the following configuration: 87KIAS, flaps up, 2600rpm, 35-inchMP, and cowl flaps open. At gross weight, flying at 6319feetasl, with an outside air temperature of 21.1C, the rate-of-climb would be 695fpm. This best rate of climb figure is predicated on the assumption that the aircraft is flying in wings-level flight. In-flight manoeuvring, such as an aggressive turn, will sharply decrease the aircraft's climb performance. Climb performance figures derived during recent flight testing indicated that the modified CessnaT207A attained a climb rate of 500fpm under normal climb configuration. The distance the aircraft would have travelled from the airport to the accident site was about 8.3nm. The climb gradient for the distance travelled is equal to 314.45feet per nautical mile. Assuming a normal climb configuration, the aircraft would have had to climb steadily at 498fpm to reach the crash site.